The invention relates to a motor bogie for a rail vehicle having an integral low-slung floor, and more particularly to a bogie having a frame resting on four wheels via a primary suspension, the frame supporting at least one motor disposed on one side of the frame and connected to at least one wheel via transmission means.
The invention is suitable in particular for trams in which a low-slung floor facilitates access (both when boarding and when alighting) for children, old people, and the disabled.
The Applicant""s Patent Application FR 2 637 861 discloses a motor bogie for a rail vehicle having a low-slung floor. That bogie has a frame resting on two axles via a primary suspension, the frame supporting traction motors disposed on the sides of the bogie and connected to the wheels via transmission means disposed outside the wheels. Unfortunately, such a bogie suffers from the drawback of having axles and axle boxes that occupy the space between the wheels, and thus make it necessary to dispose the floor above the axles.
Document EP-B1-0 698 540 discloses a motor bogie for a rail vehicle having a low-slung floor. That bogie has a frame resting on four wheels mounted individually, without being coupled together via axle shafts, and supporting two motors disposed on the sides of the bogie. Each motor has two outlet shafts connected directly to respective gear units disposed outside the wheels and connected to respective ones of the wheels via respective couplings of the hollow shaft type, allowing the wheels to be displaced vertically. Such a bogie offers the advantage of not having any axle shaft links between the individual wheels, thereby making it possible to lower the floor further, but unfortunately, it suffers from the drawback of including wheel shafts that are guided by axle boxes disposed on the insides of the wheels, thereby occupying the space between the insides of the wheels and limiting the width available for the floor at the bogies.
Such a bogie also suffers from the drawback of including braking members which are associated with the gearing and which are thus specific to a motor bogie, and the rail vehicle thus has braking members that are different on the motor bogies than on carrying bogies, thereby complicating maintenance operations.
An object of the present invention is thus to remedy the various drawbacks by proposing a motor bogie for a rail vehicle having an integral low-slung floor that makes it possible to have a floor at the bogie that extends at very low height over a width close to the spacing between the wheels. Another object of the present invention is to propose a motor bogie for a rail vehicle that has braking members that are easily accessible and that can be fitted interchangeably both to carrying bogies and to motor bogies.
The invention provides a motor bogie for a rail vehicle having an integral low-slung floor, the motor bogie having a frame resting on four wheels via a primary suspension, said frame supporting at least one motor disposed on one side of the frame and connected to at least one wheel via transmission means, wherein each wheel has an individual wheel shaft supported by an axle box, and wherein said transmission means comprise a gear unit coupled directly to the shaft of said wheel and a telescopic transmission of the type having a double universal joint and disposed between the gear unit and the motor, said gear unit being placed outside the wheel, and having a casing incorporating the axle box of the shaft of the wheel, said casing of the gear unit also serving as a support element for supporting a primary suspension member on which the frame bears.
In particular embodiments, the motor bogie of the invention may include one or more of the following characteristics taken in isolation or in any technically-feasible combination:
two motors are fixed to the frame and disposed longitudinally on either side of the frame, each motor driving the two wheels disposed one behind the other on the side of the frame, by means of a telescopic transmission of the type having a double universal joint and placed between the motor and a gear unit coupled directly to the shaft of the wheel; each gear unit having a casing incorporating the axle box of the wheel, and serving as a support element for supporting a primary suspension member;
at least one wheel has a shaft passing through the casing of the gear unit towards the outside of the bogie, said shaft of the wheel being secured to a brake disk mounted outside the gear unit;
each side of the bogie has a wheel provided with a shaft passing through the casing of the gear unit and secured to a brake disk, said brake disk being mounted outside the gear unit and on the outside of the wheel;
each of said motors has a single rotor equipped with two outlet shafts leading respectively to two opposite faces;
said members of the primary suspension are constituted by a sandwich of metal plates and of elastomer material, and they are interposed between abutment surfaces of the outside faces of the casing of the gear units and abutment surfaces of the frame; and
said frame is made up of two longitudinal sole-bars disposed outside the wheels and connected together via cross-members, each of which has a low central portion extending below the level of the axes of the wheels.